Uh, I think you don't need to calculate angle. Just normalize gap and move.
Vector pointA = Vector(1,1,1);
Vector pointB = Vector(10,10,10);
Vector gap = pointB - pointA;
// This code can occur division-by-zero error.
Vector dir = gap / sqrt(gap.x * gap.x + gap.y * gap.y + gap.z * gap.z);
float dist = 1.5;
object.position += dir * dist;